So many questions

1. During the ending scene as Jaime Pena (the detective) is recounting the day of the accident to Alex Ulloa, he makes it his mission to emphasise the fact that his wife died because Alex fled the scene, as opposed to calling for help. This will sound like a very stupid question and maybe I missed something but why was that such a point of emphasis? Couldn’t Jaime have called for help himself? He even mentions how they waited an entire hour inside the car until they were found? What was stopping Jaime from calling for help himself?
2. What in the world was the role of the hired detective Javier Alonso? Did Alex’s wife hire him or not? Was it all made up by Jaime? Is the detective even a real person? I am SO confused. If he was made up, what was the reason? Who took the photographs of Alex and Eva? Jaime also says during his monologue that Mayka knew everything? I am fully lost.
3. Who hit the guard with the car? Was it Jaime or Eva? Or both…?
4. Did Jaime and Eva plant the evidence in Alex’s car? Did Jaime move the body from the morgue to the woods? And why specifically there?
5. Was Jaime behind all the things that were happening at the morgue? (The evidence suddenly appearing inside the morgue with the TH-16 bottle, the fire alarm, the letter inside the bathroom etc). Are we supposed to believe he was leaving the scene every time, doing the deed, and coming back all whilst being noticed by no one?